What should i do? i bought a remington vantage 1200 and it seems to have a defect?

I bought the remington vantage 1200 air rifle from ***** sporting goods. A week later i realize that the mid-section wear the stock connects to the main metal piece wasn't tight and has a wobble. I haven't dropped the gun once. it has a one year warranty, but what do i do to get it fixed or get a new one.